It is mechanically possible, like this year, that parshas Vayelech is actually read twice in one year - last year it was after Rosh haShanah on Shabbos Shuvah, and this year - together with Nitzavim, ...
My question is twofold: When did we start reading a new parsha (torah portion) every week? Why did we start reading a new parsha (torah portion) every week?
I'm writing a site where the user would be able to see the calendar with jewish-civil translation of dates, and also which parasas shavua falls on which Shabbos. I'd like to know what is the formula ...